<script lang="ts">
	import { afterUpdate } from "svelte";
	import render_math_in_element from "katex/contrib/auto-render";
	import "katex/dist/katex.min.css";
	import { create_marked } from "./utils";
	import sanitize_server from "sanitize-html";
	import Amuchina from "amuchina";
	import "./prism.css";

	export let chatbot = true;
	export let message: string;
	export let sanitize_html = true;
	export let latex_delimiters: {
		left: string;
		right: string;
		display: boolean;
	}[] = [];
	export let render_markdown = true;
	export let line_breaks = true;
	export let header_links = false;
	export let root: string;

	let el: HTMLSpanElement;
	let html: string;

	const marked = create_marked({
		header_links,
		line_breaks,
		latex_delimiters
	});

	const amuchina = new Amuchina();
	const is_browser = typeof window !== "undefined";

	let sanitize = is_browser ? sanitize_browser : sanitize_server;

	function sanitize_browser(source: string): string {
		const node = new DOMParser().parseFromString(source, "text/html");
		walk_nodes(node.body, "A", (node) => {
			if (node instanceof HTMLElement && "target" in node) {
				if (is_external_url(node.getAttribute("href"))) {
					node.setAttribute("target", "_blank");
					node.setAttribute("rel", "noopener noreferrer");
				}
			}
		});

		return amuchina.sanitize(node).body.innerHTML;
	}

	function walk_nodes(
		node: Node | null | HTMLElement,
		test: string | ((node: Node | HTMLElement) => boolean),
		callback: (node: Node | HTMLElement) => void
	): void {
		if (
			node &&
			((typeof test === "string" && node.nodeName === test) ||
				(typeof test === "function" && test(node)))
		) {
			callback(node);
		}
		const children = node?.childNodes || [];
		for (let i = 0; i < children.length; i++) {
			// @ts-ignore
			walk_nodes(children[i], test, callback);
		}
	}

	const is_external_url = (link: string | null): boolean => {
		try {
			return !!link && new URL(link).origin !== new URL(root).origin;
		} catch (e) {
			return false;
		}
	};

	function escapeRegExp(string: string): string {
		return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
	}

	function process_message(value: string): string {
		let parsedValue = value;

		if (render_markdown) {
			const latexBlocks: string[] = [];
			latex_delimiters.forEach((delimiter, index) => {
				const leftDelimiter = escapeRegExp(delimiter.left);
				const rightDelimiter = escapeRegExp(delimiter.right);
				const regex = new RegExp(
					`${leftDelimiter}([\\s\\S]+?)${rightDelimiter}`,
					"g"
				);
				parsedValue = parsedValue.replace(regex, (match, p1) => {
					latexBlocks.push(match);
					return `%%%LATEX_BLOCK_${latexBlocks.length - 1}%%%`;
				});
			});

			parsedValue = marked.parse(parsedValue) as string;

			parsedValue = parsedValue.replace(
				/%%%LATEX_BLOCK_(\d+)%%%/g,
				(match, p1) => latexBlocks[parseInt(p1, 10)]
			);
		}

		if (sanitize_html && sanitize) {
			parsedValue = sanitize(parsedValue);
		}

		return parsedValue;
	}

	$: if (message && message.trim()) {
		html = process_message(message);
	} else {
		html = "";
	}

	async function render_html(value: string): Promise<void> {
		if (latex_delimiters.length > 0 && value) {
			const containsDelimiter = latex_delimiters.some(
				(delimiter) =>
					value.includes(delimiter.left) && value.includes(delimiter.right)
			);
			if (containsDelimiter) {
				render_math_in_element(el, {
					delimiters: latex_delimiters,
					throwOnError: false
				});
			}
		}
	}

	afterUpdate(async () => {
		if (el && document.body.contains(el)) {
			await render_html(message);
		} else {
			console.error("Element is not in the DOM");
		}
	});
</script>

<span class:chatbot bind:this={el} class="md" class:prose={render_markdown}>
	{@html html}
</span>

<style>
	span :global(div[class*="code_wrap"]) {
		position: relative;
	}

	/* KaTeX */
	span :global(span.katex) {
		font-size: var(--text-lg);
		direction: ltr;
	}

	span :global(div[class*="code_wrap"] > button) {
		z-index: 1;
		cursor: pointer;
		border-bottom-left-radius: var(--radius-sm);
		padding: var(--spacing-md);
		width: 25px;
		height: 25px;
		position: absolute;
		right: 0;
	}

	span :global(.check) {
		opacity: 0;
		z-index: var(--layer-top);
		transition: opacity 0.2s;
		background: var(--code-background-fill);
		color: var(--body-text-color);
		position: absolute;
		top: var(--size-1-5);
		left: var(--size-1-5);
	}

	span :global(p:not(:first-child)) {
		margin-top: var(--spacing-xxl);
	}

	span :global(.md-header-anchor) {
		/* position: absolute; */
		margin-left: -25px;
		padding-right: 8px;
		line-height: 1;
		color: var(--body-text-color-subdued);
		opacity: 0;
	}

	span :global(h1:hover .md-header-anchor),
	span :global(h2:hover .md-header-anchor),
	span :global(h3:hover .md-header-anchor),
	span :global(h4:hover .md-header-anchor),
	span :global(h5:hover .md-header-anchor),
	span :global(h6:hover .md-header-anchor) {
		opacity: 1;
	}

	span.md :global(.md-header-anchor > svg) {
		color: var(--body-text-color-subdued);
	}

	span :global(table) {
		word-break: break-word;
	}
</style>
